LeetCode 482 License Key Formatting Solution

LeetCode 482 License Key Formatting Solution in Python 3.

LeetCode 482 Solution 32 ms in Python 3

You are given a license key represented by the string s that contains only alphanumeric characters and dashes. You are also given an integer k.

Reformat the string s so that each group contains exactly k characters, except the first group that should be smaller than k but must contain at least 1 character.

Groups must be separated by dashes and all characters must be uppercase.

Analysis

First clean-up the input string s

• Remove all dashes from s,
• Convert s to uppercase.

#cleanup the input        
chars = s.upper().replace('-','')
charslen = len(chars)

Find how many whole sets of k can be found in s.

#sets and remainder
pieces = charslen // k
rest = charslen % k

Using Modulo we find the remainder after dividing the lenght of s by k.

For the first set, insert the remainder characters lenght and a dash if there are more characters left.

#start with remainder
output = chars[:rest]
output+= '-' if rest != 0 else ''

Slice the remaining string using a loop thru the sets. i*k is to jump from set to set and +rest is to offset the already used characters.

#slice the remaining string into sets
for i in range(pieces):
 output += chars[i*k+rest : (i+1)*k+rest] + '-'
 output = output[:-1] # remove the last - char

Whole Solution Code in Python 3

Code steps

class Solution:
    def licenseKeyFormatting(self, s: str, k: int) -> str:
        """
        Dragos Ion 2021
        32 ms solution
        Using Mod and Slice
        """
        #cleanup the input        
        chars = s.upper().replace('-','')
        charslen = len(chars)

        #sets and remainder
        pieces = charslen // k
        rest = charslen % k

        #start with remainder
        output = chars[:rest]
        output+= '-' if rest != 0 else ''

        #slice the remaining string into sets
        for i in range(pieces):
            output += chars[i*k+rest : (i+1)*k+rest] + '-'
        output = output[:-1] # remove the last - char

        return output